Piston for fluid-pressure engines



F. T. BURGESS PISTON FOR FLUID PRESSURE ENGINES Filed July 2'7. 1923%ZJwz 444: @M #3444 Fatentfi Got. 7, i224.

UNET@ED STATS FREDERICK TASKER BURGESS, OF LONDON, ENGLAND.

PISTON FOR FLUID-PRESSURE ENGINES,

Application filed July 27, 1923. Serial No. 654,254.

I '0 all whom it may concern:

Be it known that I, FREDERICK TASKER BURGESS, a subject of the King ofEngland, residing at London England, have invented certain new anduseful Improvements in Pistons for Fluid-Pressure Engines, of which thefollowing is a specification.

This invention relates to pistons for fluid pressure engines, and it hasfor its principal object to provide a construction which will have butsmall clearance at the skirt and thus will avoid piston slap, and alsoensure an effective scraper action on the cylinder walls. A furtherobject 'is to minimize transfer of heat from the head to the skirt.

In the accompanying drawings,

Figure 1 is a central vertical section, and

Figure 2 a horizontal section on the line 2-2 of Figure 1, illustratingone construction.

Figure 3 is a central vertical section, and

Fi re 4 a horizontal section on the line 4-4; of Figure 3,illustratingan alternative construction.

Like letters indicate like parts throughoutthe drawings.

In the construction shown in Figures 1 and 2, the web-portion is in theform of a hollow neck A of relatively small diameter where it uniteswith the crown B, but, with an easy sweep therefrom, it increases indiameter to unite with the skirt portion C, serving at the junction tostiffen the piston in bosses D thereon, and preferablymeet- 'mg theskirt at or near-the level of the piston pinraxis. In this way anannular channel E is formed between the neck and the adjacent edge ofthe skirt, and this edge is so formed as to have a scraping action whichcollects into the channel excess lubricant from the walls of thecylinder. Perforations .F ma be provided on the side or base of the cannel to allow the collected lubricant to pass to the working faces ofthe piston pin, and also to drain back to the sump.

p, e skirt of the piston is slit from end to end, in this case at twoplaces G and H oppos'ite one another and between the piston pin bosses.These slits extend into the neck A, terminating in circular holes Jdrilled or cored in the neck'at .a point between the crown and theskirt. Thus the web A is divided into two parts and resilience isimparted to the opposite sides 0" and C of the skirt which carry thebosses D not merely for a part of its length but for the whole thereof,ensuring close contact with the cylinder walls and an avoidance ofpiston bevelled edge C and C so that a scraping action takes place bothon instroke and outstroke of the piston.

The neck web portion A is made of small diameter and with thin sides andthus the passage of heat from the head ,to the skirt is minimized.

In the construction shown in Figures 3 and 4, the design issubstantially the same, but the web portion, instead of beingoriginallyof circular or similar contlnuous shape, is divided into twoseparate-webs A and A each of which unites with one skirt part. Thus theweb A? unites with the skirt art C and the web A with the skirt part Ifdesired, each web portion A or'A may be divided vertically into twoparts one lying on each side of the gudgeon pin boss F. The web portionsA and A may be curved as shown, or may be flat. According to thesectional shape the desired stiffness of the webs can be obtained, as itwill be clear that where' the webs are of curved section they arestifier than where they are of flat formation.

Preferably in each case the webs A and A incline towards one another atthe top, so that when the piston is under load the tendency is for theskirt parts C and C, to spread and to work closely in the cylinderbore.'

Although it has been stated that the skirt parts in both constructionsare separated from one another, as by the slits H, .-m some designs,where the piston pin bosses F are low down, it might not be essentialthat the skirt portion should be slit from end to end, and I wish tomake it clear that .my invention covers constructions in which the skirtis split substantially fromend to end so that t e desired separatingefiect of the skirt side can be obtained.

Again, in some cases the skirt may be split-at a single point betweenthe piston pin bosses, the skirt being still free to expand and thebosses to move towards and away from one another, as will be readilyunderstood.

In the construction shown in Figures 3 and 4 the skirt is formed with anumber of grooves C and oil holes'C whilst the edges C and C are sobevelled as to encourage theoil to flow alongthe'skirt and pass away tothe interior through the grooves C and holes C. g

In manufacturing a piston of this kind in aluminium alloy, the skirt canbe machined cylindrical to the exact bore of the cylinder, or with onlya very small running clearance, such as is used with pistons having castiron skirts. If the fit is too tight the skirt will contract slightly,but if too loose it will "expand,- and, during the firing stroke, andprobably also during the compression stroke, when the loads are hi hest,the pressure on the crown causes the ower ends of the webs to tend tospread, so that any clearance is taken up and the skirt fits thecylinder the whole way round, ensuring distribution of the wear andabsence of noise. In addition, it will be clear that there can be noslap or noise of the piston in the cylinder walls and that, in spite ofthe close fit, seizure of the piston is pre-' vented owing to itsability to yield inwards. Again, distortion of the skirt in theneighbourhood of the piston bosses is reduced to will fit worn orover-size cylinders, which is a-great saving in repair work.

What I claim as my invention and desire to secure by Letters Patent ofthe United States is I 1. In a piston, in combination, a crown, aseparate expansible skirt having bosses for the piston pin, inclinedwebs connecting the crown and the skirt in such a manner that pressureon; the crown causes expansion of the skirt. I

2. In a piston, in combination, a crown,

a separate skirt divided into two parts by longitudinal slits, a pistonpin boss in each part, a web portion connecting each part of the skirtto the underside of the crown, uniting with the skirt parts close to thepiston pin bosses and forming the sole connection between the crown andskirt.

.3. In a piston, in combination, a crown, a separate two part skirt, apiston pin boss in each part, an inclined web portion connecting eachpart of the skirt to the underside of the crown and forming the soleconnection between said parts.

4. In a piston, in combination, a crown,

a separate expansible skirt having bosses for the piston pin, inclinedcurved webs connecting the crown and the skirt in such a manner thatpressure on the crown causes expansion of the skirt.

5. In a piston, in combination, a crown, a se arate skirt divided intotwo parts by longitudinal slits, a piston pin boss in each part, acurved web portion connecting each part of the skirt to the underside ofthe crown, uniting with the skirt parts close to thepiston pin bossesand forming the sole connection between the crown and skirt.

In testimony whereof I afiix my signature.

FREDERICK IASKIER BURGES.

